Primary exercises
- Manually created factor.
In a study participants were asked whether their sport activity is none, oncePerWeek, severalPerWeek or daily.
Build a proper factor for the responses below and store it in a variable w.
Print the factor.
Write the code to count the numbers of occurrences of each level and print the counts.
severalPerWeek, none, none, oncePerWeek, oncePerWeek, oncePerWeek, oncePerWeek, ?, none, none
v <- c( "severalPerWeek", "none", "none", "oncePerWeek", "oncePerWeek", "oncePerWeek", "oncePerWeek", NA, "none", "none" )
w <- factor( v, levels = c( "none", "oncePerWeek", "severalPerWeek", "daily" ) )
w
[1] severalPerWeek none none oncePerWeek oncePerWeek oncePerWeek oncePerWeek <NA> none
[10] none
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 5 x 2
f n
<fct> <int>
1 none 4
2 oncePerWeek 4
3 severalPerWeek 1
4 daily 0
5 <NA> 1
- A factor with a random content.
Read help about the function sample.
Then study and try the following lines of code to understand the results.
Next, understand why an error is generated and use replace argument to generate a vector with 100 samples.
Store this vector in a variable v and build a factor w from it.
Finally, count the numbers of occurrences of each level in w.
Ensure, that levels are in order provided in the variable lvl.
lvs <- c( "none", "oncePerWeek", "severalPerWeek", "daily" )
sample( lvs, 3 )
[1] "none" "oncePerWeek" "severalPerWeek"
sample( lvs, 3 )
[1] "severalPerWeek" "none" "oncePerWeek"
sample( lvs, 3 )
[1] "daily" "oncePerWeek" "none"
sample( lvs, 100 )
Error in sample.int(length(x), size, replace, prob): cannot take a sample larger than the population when 'replace = FALSE'
v <- sample( lvs, 100, replace = TRUE )
w <- factor( v, levels = lvs )
w
[1] daily oncePerWeek oncePerWeek none severalPerWeek daily daily none daily
[10] daily oncePerWeek oncePerWeek oncePerWeek severalPerWeek severalPerWeek oncePerWeek oncePerWeek severalPerWeek
[19] none oncePerWeek severalPerWeek severalPerWeek severalPerWeek severalPerWeek oncePerWeek daily none
[28] severalPerWeek daily daily daily oncePerWeek none oncePerWeek none none
[37] oncePerWeek oncePerWeek daily none daily daily none severalPerWeek oncePerWeek
[46] oncePerWeek daily oncePerWeek daily none oncePerWeek daily oncePerWeek none
[55] none daily severalPerWeek daily none daily oncePerWeek none oncePerWeek
[64] daily oncePerWeek daily oncePerWeek daily daily daily none none
[73] oncePerWeek none oncePerWeek oncePerWeek severalPerWeek none daily daily severalPerWeek
[82] severalPerWeek daily none severalPerWeek severalPerWeek daily oncePerWeek severalPerWeek none
[91] none oncePerWeek severalPerWeek severalPerWeek severalPerWeek daily none daily none
[100] severalPerWeek
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 4 x 2
f n
<fct> <int>
1 none 23
2 oncePerWeek 27
3 severalPerWeek 21
4 daily 29
- Reordering factor levels.
When a factor is shown on an axis of a plot, the order is given by its levels.
The factor w from the previous exercise will be then shown in this order: none, oncePerWeek, severalPerWeek, daily.
But for a picture in a manuscript the following order might be needed: daily, severalPerWeek, oncePerWeek, none.
Apply to w one of the fct_ functions from the tidyverse library to produce a factor w2 with the requested order.
Show the levels of w2.
Again show the number of elements of each level in w2 and compare it with the table of the previous exercise.
w2 <- fct_relevel( w, c( "daily", "severalPerWeek", "oncePerWeek", "none" ) )
levels( w2 )
[1] "daily" "severalPerWeek" "oncePerWeek" "none"
fct_count( w2 )
# A tibble: 4 x 2
f n
<fct> <int>
1 daily 29
2 severalPerWeek 21
3 oncePerWeek 27
4 none 23